The invention relates to a process for producing a composite cast part containing an insert part and casting material, wherein the insert part is integrally bonded to the casting material.
The production of composite cast parts makes it possible to combine the preferred properties of the materials at the appropriate points. Thus, components can be assembled optimally according to their requirements and fields of use on account of the material combination. However, this requires an integral or metallurgical bond between the materials. When casting steel parts into cast iron or aluminium alloys, there is often the problem of an inadequate bond between the steel part cast in and the surrounding or cast-in material. The early solidification of the molten mass on account of the contact with the insert part at room temperature hinders a metallurgical or integral bond between the casting material and the steel part, as a result of which gaps can form between the composite partners.
DE 10 2006 041 901 A1 discloses a process for producing metallic composite parts made of steel and/or cast iron. In this process, the part to be cast in, which is produced from steel or cast iron, is coated by means of flux. The aim of the coating is to reduce the oxide skin of the cast-in part, that is to say that the oxide skin of the cast-in part is dissolved and washed away during the casting-in process, as a result of which the casting material can enter into a metallurgical bond.
DE 10 2011 053 858 B3 discloses a process for the use of a component which can be cast in a lost casting mould, wherein a coating agent is applied to a surface of the component to be cast in. The coating agent forms an actively separating surface which prevents the adhesion of the material on the component and also corrosion before encapsulation with casting material.
DE 100 43 105 B4 discloses a process for forming a strong, tough, resilient and/or at least substantially flawless bond between an insert and a casting metal material having a melting point below that of the insert material. The insert is coated with a thin layer of a metallic material which is selected from the group consisting of silver, antimony, bismuth, chromium, gold, lead, magnesium, silicon, tin, titanium and zinc. Thereafter, the casting material is cast against the coated surface of the insert. The coefficient of thermal expansion of the coating is greater than that of the insert and less than that of the casting material. The coated insert is moreover held at a temperature of at least 100° C. for a period of time of at least 5 minutes. As a result of this process, part of the coating should dissolve and be sacrificed to the casting metal material, while part of this coating remains as a diffusion barrier between the insert and the casting material, which should achieve a highly tough bond between the insert and the casting material.
It is an object of the present invention to provide a process and a corresponding composite cast part which, compared to the prior art, achieves an improved bond between an insert part and casting material and also ensures economical production.